The tremendous popularity of the World Wide Web has presented a number of challenges to web site administrators. As the number of computer users having access to web browsers increases, web site administrators constantly work to improve the efficiency of their web sites in the face of explosive growth in both the number of users visiting their site and the sheer quantity of information being provided. Many web site administrators have discovered that a single web server computer can not perform the tasks necessary to receive and fulfill requests from users browsing their site, no matter how well the web server computer is optimized.
One way web site administrators address the challenges presented by massive numbers of browsing users is by placing content on a computer separate from the web server by using a facility called “virtual directories.” The virtual directory feature is supported by MICROSOFT Internet Information Server (IIS), a product available from Microsoft Corporation of Redmond, Wash. One aspect of a virtual directory allows a web site administrator to redirect requests for information (e.g., web pages in “http://a.b.com/products/”) to a server separate from the web server. The web site administrator configures such a system by creating a virtual directory and specifying the location from which the information is to be drawn for the virtual directory.
The web site administrator can then deploy several web servers on several machines, all drawing content from a content server running on yet another machine. Requests for information can be divided among the several web servers via a routing mechanism. In this way, the web servers can be optimized to field requests for content, and the content server can be optimized to serve content. The content server need not provide full web server functionality, and its computing resources can be devoted to serving content, leading to greater availability of the data.
Still, however, the content is being drawn from a single content server. As the amount of data increases, the single content server becomes overwhelmed. Web site administrators have responded by creating multiple virtual directories and pointing them to multiple different servers. The administrator can then scatter the site's web pages over multiple content servers by placing them in different virtual directories. When a request for a web page comes in to the web site, the software fielding the request at a web server maps the requested page's location (e.g., “products”) to virtual directory information, which specifies on which content server the content resides. Web site administrators thus attempt to avoid overload of any single machine by directing only a percentage of the incoming requests for web pages to any one content server.